• Proceedings of the PSK Conference
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• 2001.04a
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• pp.224.1-224.1
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• 2001

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.163-167
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• 2017

Utilizing a unique capability of AKARI that allows deep spectroscopy at $2.5-5.0{\mu}m$, we performed a spectroscopy study of more than 200 quasars through one of the AKARI mission programs, QSONG (Quasar Spectroscopic Observation with NIR Grism). QSONG targeted 155 high redshift (3.3 < z < 6.42) quasars and 90 low redshift active galactic nuclei (0.002 < z < 0.48). In order to provide black hole mass estimates based on the rest-frame optical spectra, the high redshift part of QSONG is designed to detect the $H{\alpha}$ line and the rest-frame optical spectra of quasars at z > 3.3. The low redshift part of QSONG is geared to uncover the rest-frame $2.5-5.0{\mu}m$ spectral features of active galactic nuclei to gain useful information such as the dust-extinction-free black hole mass estimators based on the Brackett lines and the temperatures of the hot dust torus. We outline the program strategy, and present some of the scientific highlights from QSONG, including the detection of the $H{\alpha}$ line from a quasar at z > 4.5 which indicates a rigorous growth of black holes in the early universe, and the $Br{\beta}$-based black hole mass estimators and the hot dust temperatures (~ 1100 K) of low redshift AGNs.

• Journal of electromagnetic engineering and science
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• v.11 no.1
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• pp.42-50
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• 2011

One of the important applications of THz time-domain spectroscopy (TDS) is the detection of explosive materials through identification of vibrational fingerprint spectra. Most recent THz spectroscopic measurements have been made using pellet samples, where disorder effects contribute to line broadening, which results in the merging of individual resonances into relatively broad absorption features. To address this issue, we used the technique of parallel plate waveguide (PPWG) THz-TDS to achieve sensitive characterization of three explosive materials: TNT, RDX, and HMX. The measurement method for PPWG THz-TDS used well-established ultrafast optoelectronic techniques to generate and detect sub-picosecond THz pulses. All materials were characterized as powder layers in 112 ${\mu}m$ gaps in metal PPWG. To illustrate the PPWG THz-TDS method, we described our measurement by comparing the vibrational spectra of the materials, TNT, RDX, and HMX, applied as thin powder layers to a PPWG, or in conventional sample cell form, where all materials were placed in Teflon sample cells. The thin layer mass was estimated to be about 700 ${\mu}g$, whereas the mass in the sample cell was ~100 mg. In a laboratory environment, the absorption coefficient of an explosive material is essentially based on the mass of the material, which is given as: ${\alpha}({\omega})=[ln(I_R({\omega})/I_S({\omega}))]m$. In this paper, we show spectra of 3 different explosives from 0.2 to 2.4 THz measured using the PPWG THz-TDS.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.820-828
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• 2018

The growing nuclear threat has amplified the need for developing diverse and accurate nuclear forensics analysis techniques to strengthen nuclear security measures. The work presented here is part of a research effort focused on developing a methodology for reactor-type discrimination of weapons-grade plutonium. To verify the developed methodology, natural $UO_2$ fuel samples were irradiated in a thermal neutron spectrum at the University of Missouri Research Reactor (MURR) and produced approximately $20{\mu}g$ of weapons-grade plutonium test material. Radiation transport simulations of common thermal reactor types that can produce weapons-grade plutonium were performed, and the results are presented here. These simulations were needed to verify whether the plutonium produced in the natural $UO_2$ fuel samples during the experimental irradiation at MURR was a suitable representative to plutonium produced in common thermal reactor types. Also presented are comparisons of fission product and plutonium concentrations obtained from computational simulations of the experimental irradiation at MURR to the nondestructive and destructive measurements of the irradiated natural $UO_2$ fuel samples. Gamma spectroscopy measurements of radioactive fission products were mostly within 10%, mass spectroscopy measurements of the total plutonium mass were within 4%, and mass spectroscopy measurements of stable fission products were mostly within 5%.

• Mass Spectrometry Letters
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• v.10 no.1
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• pp.32-37
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• 2019

The ${\pi}-{\pi}$ interactions of the peptide-dimer and peptide-trimer complexes were investigated in the (VQIVYK + LYQLEN) and (VQIVYK + NNQQNY) mixing solutions. The results showed that tyrosine (Y) residues were critical in the formation of hetero peptide-dimers and -trimers during the early oligomerization process. We used collision-induced dissociation (CID) along with electrospray ionization mass spectroscopy (ESI-MS) to obtain the structural information of the hetero-dimers and -trimers. We chose three amyloidogenic peptides-VQIVYK, NNQQNY, and LYQLEN-from tau protein, yeast prion-like protein Sup35, and insulin chain A, respectively. Hetero-dimer, -trimer, -tetramer, and -pentamer complexes were observed in the mass spectra. The tandem mass spectrum of the hetero-dimer and hetero-trimer showed two different fragmentation patterns (covalent and non-covalent bond dissociation). Y-Y interaction structures were also proposed for the hetero-dimer and -trimer complexes.

• Journal of the Korean Applied Science and Technology
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• v.38 no.3
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• pp.824-831
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• 2021

1, 2-Octanediol galactoside (OD-gal) has been synthesized from 1, 2-octanediol (OD), as a safer cosmetic preservative, using recombinant Escherichia coli β-galactosidase (β-gal). To confirm the molecular structure of synthesized OD-gal, mass spectrometry and NMR (¹H- and ¹³C-) spectroscopy of OD-gal were carried out. In the reaction mixture, a sodium adduct ion of OD-gal (m/z=331.1732) was identified using mass spectrometry analysis. In addition, ¹H NMR spectrum of OD-gal showed multiple peaks corresponding to the galactosyl group, which is evidence of galactosylation on OD. Downfield proton peaks at δ_H 4.39 ppm and multiple peaks from δ_H 3.98~3.55 ppm were indicative of galactosylation on OD. Up field proton peaks at δ_H 1.52~1.26 ppm and 0.89 ppm showed the presence of CH₂ and CH₃ protons of OD. ¹³C NMR spectrum revealed the presence of 24 carbons suggestive of α- and β-anomers of OD-gal. Among 14 carbon peaks from each anomer, the 4 peaks at δ_C 31.4, 29.0, 22.3, and 13.7 ppm were assigned to be overlapped showing only 24 peaks out of a total of 28 peaks. The mass value from mass spectrometry analysis of OD-gal, and ¹H and ¹³C NMR spectral data were in good agreement with the expecting structure of OD-gal. Finally, we identified a galactose molecule from the hydrolysate of OD-gal using β-gal. We are expecting that through future study it will eventually be able to develop a safe cosmetic preservative.

• Investigative Magnetic Resonance Imaging
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• v.8 no.2
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• pp.86-93
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• 2004

Purpose: We evaluated $^1H$ MR spectroscopy improves the preoperative diagnosis of diffuse infiltrative type of primary central nervous system lymphomas. Materials and methods: After review of conventional MR images and medical records, we retrospectively reviewed proton MR spectra in seven patients with primary central nervous system lymphoma diagnosed by means of biopsy. Relative ratio of choline (Cho), N-acetylaspartate (NAA), and lipid-lactate (Lip-Lac) to creatine (Cr) were measured for quantitative analysis. Results: The average ratio of Cho/Cr was $1.80{\pm}0.95$, NAA/Cr was $1.34{\pm}0.41$, and Lip-Lac/Cr was $1.12{\pm}0.16$. All cases of lymphomas showed increased Lip-Lac peak. Two case of mass forming lymphoma showed decreased NAA/Cr significantly, whereas five cases of lymphoma without mass formation showed preserved NAA/Cr. Conclusion : We thought the presence of Lip-Lac peak without significant reduction of NAA on the MR spectroscopy was helpful for diagnosis of diffuse infiltrative type of central nervous system lymphoma.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.55-60
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• 2001

The effect of high energy B ion implantation and initial oxygen concentration upon defect formation and gettering of metallic impurities in Czochralski silicon wafer has been studied by applying DLTS( Deep Level Transient Spectroscopy), SIMS(Secondary ton Mass Spectroscopy), BMD (Bulk Micro-Defect) analysis and TEM(Transmission Electron Microscopy). DLTS results show the signal of the deep levels not only in as-implanted samples but also in low and high temperature annealed samples. Vacancy-related deep levels in as- implanted samples were changed to metallic impurities-related deep levels with increase of annealing temperature. In the case of high temperature anneal, by showing the lower deep level concentration with increase of initial oxygen concentration, high initial oxygen concentration seems to be more effective compared with the lower initial oxygen one.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.832-839
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• 1992

Lead has been determined by Resonance Ionization Mass Spectrometry (RIMS) through one-color-two-photon ionization, two-color-two-photon ionization and three-color-three-photon ionization in a vacuum chamber equipped with Time-of-Flight(TOF) mass spectrometer. In all cases, the first excited state chosen was 6p7s($^3P_1$) state and the transition was at 283.3 nm in wavelength from the ground state. By using various concentrations of lead standard solutions, the calibration curve is obtained in the range of 0.1 ${\mu}g$ to 1.0 pg in both ionization schemes. The detection limit was estimated as 20 pg for the two-color ionization, while 10 pg for the three-color ionization experiment.

• Journal of Applied Biological Chemistry
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• v.64 no.4
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• pp.363-368
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• 2021

The fruits of tomato (Lycopersicon esculentum) were extracted with 70% aqueous methanol (MeOH) and the concentrates were partitioned into ethyl acetate (EtOAc), n-butanol (n-BuOH), and water (H₂O) fractions. The repeated silica gel (SiO₂) and octadecyl silica gel column chromatographies for the EtOAc fraction, whose activity was confirmed, led to isolation of one flavone compound. Nuclear magnetic resornance, infrarad spectroscopy, and mass spectroscopy (MS) revealed the chemical structure of the isolated compound, 5,7,3'-trihydroxy-6,4',5'-trimethoxyflavone (1). LC-MS/MS analysis determined the content level of compounds 1 in the MeOH extract to be 4.02±0.12 ㎍/mg and in the TME-10 fraction to be 0.96±0.03 ㎍/mg. Through this study, the antioxidantive capacity was confirmed by demonstrating that the L. esculentum extract and their fractions showing an increase in glutathione mean and a decrease in glutathione heterogeneity uniformly raises the intracellular glutathione level.